The present invention relates to replenisher systems in processors of photosensitive material. In particular, the present invention relates to an improved control system which is particularly useful in providing appropriate amounts of anti-oxidation (A-O) replenishment.
It is well known that photographic processors require replenishment of the processing fluids to compensate for changes in the chemical activity of the fluids. First, it has been recognized that replenishment is necessary to replace constituents used as photosensitive film or paper is developed in the processor. This replenishment is "use-related" or "exhaustion" chemical replenishment. Second, some replenishment systems have provided additional replenishment of an "anti-oxidation" (A-O) replenishment solution which counteracts the deterioration in chemical activity of the processor fluids due to aerial oxidation, which occurs with the passage of time regardless of whether film or paper is being processed.
Replenishment systems were originally manually operated. The operator would visually inspect the film being processed and would manually operate a replenisher system as he deemed necessary. The accuracy of manual replenisher systems is obviously dependent upon the skill and experience of the operator.
Various automatic chemical replenishment systems have been developed for providing "use-related" replenishment. Examples of these automatic replenishment systems include U.S. Pat. Nos. 3,592,539 by Schumacher; 3,559,555 by Street; 3,561,344 by Frutiger; 3,696,728 by Hope; 3,752,052 by Hope et al; 3,927,417 by Kinoshita et al; 4,057,818 by Gaskell et al; and a 4,104,670 by Charnley and Kumpula, which is assigned to the same assignee as the present application.
An example of a prior art replenisher control for providing both use-related and anti-oxidation replenishment is shown in U.S. Pat. No. 3,822,723 by Crowell et al. This patent shows the coordination of use-related and anti-oxidation replenishment by means of an electro-mechanical control system. The Crowell et al system, with its use of analog electronics and electro-mechanical cams, is generally difficult to calibrate, subject to drift problems, and is relatively limited in the number of control options available to the user. There is a continuing need for simpler, more reliable automatic replenisher systems which provide accurate anti-oxidation replenishment.